Whey protein solids, such as spray-dried sweet whey or acid whey, delactosed whey, and whey protein concentrate, have been used to provide part or all of the protein and lactose solids in media for preparing bulk starter cultures in the manufacture of cheese. After preparation, the media are inoculated with the lactic acid-producing bacteria desired for manufacturing the particular cheese, and the bacteria are cultured therein to produce the starter culture for addition to the milk in the cheese vat. The whey protein does not coagulate in the cheese vat with the casein, but part of the protein of the starter media will be in a denatured or precipitated form, which can become associated with the coagulated casein by physical entrapment. By the mixing and stirring of the curd in the cheese vat, most of the precipitated protein of the starter culture, as well as the small fragments of curd released during cutting and stirring (referred to as "curd dust" or "fines") can be removed from the curd and will pass out of the vat with the whey. When the whey is passed through a screen, as is conventional practice, the curd dust or fines accumulate on the screen, but complete removal of the smaller sized fines is not obtained. An additional pre-filtration step is therefore required when the whey is to be subjected to ultrafiltration.
It would therefore be desirable to provide a method for preparing substantially fine-free starter media from whey solids, and especially if the whey protein will coagulate with the casein in the cheese vat forming a true total coagulum. The quantity of cheese produced would thereby be increased, there would be no entrapment of precipitated protein which was not in the proper coagulated form, and there would be greater reduction of fines amount as well as an improvement in the quality of the fines, i.e., the fines would more nearly resemble true cheese curd. Heretofore, however, the art has failed to provide such a method.
In preparing bulk starter cultures, whey solids have been combined with milk solids. See U.S. Pat. Nos. 3,852,158, 4,020,185 and 3,998,700. Yogurt has also been prepared by using mixtures of whey protein and milk solids, as described in U.S. Pat. No. 4,110,476. The latter patent discloses that the whey proteins are utilized to protect the casein of the milk protein against coagulation during the manufacture of the liquid yogurt.
Interactions of casein with serum protein have been described in the literature. See Fundamentals of Dairy Chemistry (2nd Ed., 1974), Chapt. 11, 628-631. Whey protein is comprised of serum protein, namely, the lactalbumins and lactoglobulins. Commercial applications of the interaction or "complexing" of casein and serum protein or whey protein have been proposed. See French Pat. No. 1,528,103; Polish Pat. No. 82,699; and Schw. Milch. Forsch., 4, 1-8 (1975). As described in the cited French patent, a calcium salt is added to milk, which is then heated to a temperature at which the complex of casein and serum protein precipitates. The Polish patent proposes the addition of a calcium salt to milk, which is then pasteurized to complex the casein and whey protein, and then used to prepare cheese in the usual way by the addition of a starter culture and rennet. The last-cited reference proposes the addition of whey, such as a whey protein concentrate, to milk. After addition of calcium chloride the milk-whey mixture is heated to complex the casein and whey protein, which is then coagulated, corresponding to rennet coagulation in the manufacture of cheese.